The invention relates to an air intake system of an internal-combustion engine having at least one bank of cylinders in which the intake air flows from an air filter to each bank of cylinders through a measuring device preferably constructed as an air mass sensor and through a throttle housing and from there is guided into a collecting tank which is connected to a cylinder head of the internal-combustion engine by means of suction pipes.
An air intake system having two collecting tanks which are designed as resonance tanks and are connected with one another are known from the German Patent Document DE 34 24 433. In this case, the flow cross-section from one resonance tank to the next resonance tank may be changed by connecting bypass pipes by means of throttle valves. The resulting torque increase may therefore be displaced to different rotational speed ranges.
From the German Patent Document DE-GM 16 69 265, a collecting tank is known which is constructed as a suction manifold which takes in air by way of up to three physically separated inlet openings. These inlet openings are not connected with one another outside the suction manifold and, together with nozzle-type pipes disposed in front of them, are used only as intake noise dampers.
During the operation of an internal-combustion engine, a vacuum occurs at the inlet side as a result of the suction of the individual cylinders; i.e., a demand for air is created in the intake system which increases as the rotational speed increases.
It is an object of the invention to design an air intake system of an internal-combustion engine such that an increase in power and torque is achieved.
This object is achieved by means of an arrangement wherein a branching is arranged between the throttle housing and the collecting tank, from which branching several pipe sockets are connected to the collecting tank in such a manner that the intake air flows into the collecting tank from different directions.
The air intake system according to the invention provides an arrangement in which the air flow which flows from the air filter in a single flow, by means of a measuring device which preferably is constructed as an air mass flow sensor, is branched downstream of the air flow sensor and subsequently, in several flows, is supplied to an individual collecting tank. Individual suction pipes lead from there to the inlet ducts in the cylinder head of the internal-combustion engine. Advantageously, the branching of the intake air, which at first flows through a common pipe, into several partial flows which lead into the collecting tank at physically separate points, results in a clear increase of power and torque over a wide rotational-speed range of the internal-combustion engine.
This increase occurs preferably in internal-combustion engines where the time intervals between the intake strokes are relatively large so that pronounced pressure fluctuations build up in the intake system. This occurs in the case of four-cylinder in-line internal-combustion engines or, for example, in the case of 8-cylinder V-engines with a 180.degree. spark gap. In this case, a separate air intake system is assigned to each cylinder bank.
In the case of the air intake system according to the invention, a direct intake line as well as at least one bypass line leads from the branching into the collecting tank.
In this type of a construction, it was found that a harmonic pressure oscillation occurs along the whole intake path of the air, that is, from the air filter to the inlet valves of the internal-combustion engine, which is in phase with the piston movement in the cylinders of the internal-combustion engine. Compared with known constructions, several advantages are therefore obtained. On the one hand, at the start of each inlet stroke, a lower pressure exists in front of the respective inlet valve which corresponds almost to the pressure in the cylinder, and which therefore is in phase with the pressure course in the cylinder. Furthermore, at the point in time of a maximum piston speed, a higher flow rate exists along the whole length of the suction pipes from the collecting tank to the inlet valve. As a result, a larger amount of air flows to each cylinder. Finally, at the end of the inlet stroke, when the inlet valve reduces the inlet cross-section, a higher pressure exists along the whole length of the suction pipes which results in a better cylinder charging.
In addition, this bypass line requires no control because it connects and disconnects itself because of the geometric design. By means of the connecting of more than one bypass line and its design for various rotational speeds of the internal-combustion engine, an increase of power and torque can be achieved over a wider rotational-speed range. The individual bypass lines are connected during the run through the rotational-speed range of the internal-combustion engine; they reach their maximum contribution to the pressure increase at the respective coordinated rotational speed; and are disconnected again when the rotational speed is increased further.
The invention therefore distinguishes itself by a simple construction. Compared to known intake systems which are controlled by means of several throttle valves and are designed for a tuned intake pressure charging, the invention clearly has fewer parts and therefore has advantages with respect to cost, servicing and weight.
Preferred embodiments of the invention include other advantageous features. In certain embodiments, a branching of the intake air at a small angle which should not exceed 45.degree. leads to optimal results. Equally advantageous is a respective vertical flowing of the intake air into the collecting tank. When two flows flow into the collecting tank, the two flow-in points should be opposite one another; in the case of a three-flow construction, the third flow-in point should be situated perpendicularly with respect to the two flow-in points which are opposite one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.